Accession Number:

ADA160737

Title:

Electromagnetic Measurements of Multi-Year Sea Ice Using Impulse Radar,

Descriptive Note:

Corporate Author:

COLD REGIONS RESEARCH AND ENGINEERING LAB HANOVER NH

Personal Author(s):

Report Date:

1985-09-01

Pagination or Media Count:

33.0

Abstract:

Sounding of multi-year sea ice, using impulse radar operating in the 80- to 500-MHz frequency band, has revealed that the bottom of this ice cannot always be detected. This paper discusses a field program aimed at finding out why this is so, and at determining the electromagnetic EM properties of multi-year sea ice. It was found that the bottom of the ice could not be detected when the ice structure had a high brine content. Because of brines high conductivity, brine volume dominates the loss mechanism in first-year sea ice, and the same was found true for multi-year ice. A two-phase dielectric mixing formula, used by the authors to describe the EM properties of first-year sea ice, was modified to include the effects of the gas rockets found in the multi-year sea ice. This three-phase mixture model was found to estimate the EM properties of the multi-year ice studied over the frequency band of interest. The latter values were determined by 1 verified sounding to a subsurface target of known depth, where the two-way travel time of the EM wavelet in the ice is measured 2 cross-borehole transmission, where the transit time of the EM wavelet is measured through a known thickness of sea ice and 3 a wide-angle or common-depth-point reflection method. Preliminary findings also indicate that a representative value for the apparent bulk dielectric constant of multiyear sea ice over 2 12 m thick is 3.5. Keywords includ Cold regions, Electromagnetic properties, Marine geophysics, and Sea ice.

Subject Categories:

  • Snow, Ice and Permafrost
  • Active and Passive Radar Detection and Equipment
  • Electricity and Magnetism

Distribution Statement:

APPROVED FOR PUBLIC RELEASE